Divalent lanthanide complexes: highly active precatalysts for the addition of N-H and C-H bonds to carbodiimides.
Various divalent lanthanide complexes with the formula LnL2(sol)x (L = N(TMS)2, sol = THF, x = 3, Ln = Sm (I), Eu (II), Yb (III); L = MeC5H4, sol = THF, x = 2, Ln = Sm (IV); L = ArO(Ar = [2,6-((t)Bu)2-4-MeC6H2]), sol = THF, x = 2, Ln = Sm (V)), especially complexes I- III, serve as excellent catalyst precursors for catalytic addition of various primary and secondary amines to carbodiimides, efficiently providing the corresponding guanidine derivatives with a wide range of substrates under solvent-free condition. The reaction shows good functional groups tolerance. Complexes I- III are also excellent precatalysts for addition of terminal alkynes to carbodiimides yielding a series of propiolamidines. The active sequence of Yb < Eu < Sm for metal and MeC5H4 < ArO < N(TMS)2 for ligand around the metal was observed for both reactions. The first step in both reactions was supposed to include the formation of a bimetallic bisamidinate samarium species originating from the reduction-coupling reaction of carbodiimide promoted by lanthanide(II) complex. The active species is proposed to be a lanthanide guanidinate and a lanthanide amidinate.
Du
Zhu
Z
Key Laboratory of Organic Synthesis of Jiangsu Province, Department of Chemistry and Chemical Engineering, Suzhou University, Dushu Lake Campus, Suzhou University, Suzhou 215123, People's Republic of China.
Li
Wenbo
W
Zhu
Xuehua
X
Xu
Fan
F
Shen
Qi
Q
D000480:Alkynes / Q000737:chemistry; D000588:Amines / Q000737:chemistry; D002234:Carbodiimides / Q000737:chemistry*; D002244:Carbon / Q000737:chemistry*; D002384:Catalysis; D006859:Hydrogen / Q000737:chemistry*; D028581:Lanthanoid Series Elements / Q000737:chemistry*; D008024:Ligands; D009584:Nitrogen / Q000737:chemistry*; D011522:Protons
D000480:Alkynes; D000588:Amines; D002234:Carbodiimides; D028581:Lanthanoid Series Elements; D008024:Ligands; D011522:Protons; D002244:Carbon; D006859:Hydrogen; D009584:Nitrogen